The present invention relates to automatic transmission systems and, more particularly, to improvements in a torque converter clutch (hereinafter “TCC”) solenoid assembly for use in General Motors 4L60-E and other similar transmissions.
The General Motors 4L60-E (hereinafter “GM”) transmission and other similar GM transmissions are equipped with mechanisms to “lockup” their torque converters to varying degrees under certain operating conditions. The purpose of the lockup converter is to provide for direct drive when the vehicle is cruising at higher speeds. Since there is always some slippage in the fluid coupling of a torque converter, some power is lost and fuel economy suffers. By providing a direct mechanical coupling through the transmission at high engine speeds, the lockup converter improves fuel economy.
This is accomplished by an electronic/hydraulic torque converter clutch system, which utilizes a lockup piston within the torque converter housing. The lockup piston has friction material on its forward surface. When the vehicle is at cruising speed and lockup is desired, an electric solenoid is energized, which opens the Torque Converter Clutch (hereinafter “TCC”) Regulator Valve. This allows fluid pressure to act upon the lockup piston, which is forced against a machined surface on the converter cover. Thus, the lockup piston and the converter cover are locked together and act as a single unit similar to a manual transmission clutch. When lockup is no longer required, a port opens that allows the pressurized fluid to exhaust. The lockup piston then moves away from the torque converter housing re-establishing the fluid coupling.
In the GM 4L60-E transmission fluid pressure to the torque converter clutch is controlled by a pulse width modulated (hereinafter “PWM”) solenoid (i.e. PWM TCC solenoid) that provides an output or control pressure in response to the duty cycle imposed on the solenoid coil. The PWM TCC solenoid sends automatic transmission fluid (hereinafter “ATF”) to the TCC Regulator valve, which regulates it to a lesser pressure that is known as converter clutch (CC) signal pressure. Converter clutch signal pressure is not actually sent to the torque converter, but to the Converter Clutch Valve 200 (hereinafter “TCC Apply Valve”) as shown in FIG. 1. The TCC Apply Valve 200 is actuated by a separate TCC solenoid 100. The Powertrain Control Module (hereinafter “PCM”) (not shown) controls the TCC solenoid 100 (FIG. 1) to apply and release the torque converter clutch. The TCC solenoid 100 is a normally open, ON/OFF type solenoid that, when energized, initiates the converter clutch apply cycle.
A problem exists in the original equipment manufacture (hereinafter “OEM”) TCC solenoid assembly 100 and, more particularly, in the solenoid snout 150, which conducts converter clutch signal fluid as at 145 (FIG. 1) to exhaust when the TCC solenoid 100 is in the OFF or release mode. The OEM solenoid snout 150 is fabricated from molded plastic material, which is subject to stress cracks that cause ATF leakage and improper functioning of the TCC apply valve 200.
In addition, an OEM TCC signal orifice check valve, indicated generally at 148, is installed in the converter clutch signal circuit 145 (FIG. 1) to control converter drain back when the vehicle is turned off. This miniature check valve 148 includes a plastic, capsule-type housing that is pressed into the converter clutch signal circuit 145 within the pump assembly 130. It is not uncommon for the OEM check valve 148 to be dislodged from its functional position and to be carried downstream under fluid pressure into the TCC apply valve 200 where it becomes jammed causing malfunction of the torque converter clutch.